Another thing is that they have to be perfectly fitted to the horse. A lot of people have the noseband too low, and this can crush the delicate cartilage of the nose. It must ride higher up on the bone structures.
Mechanical hacks that have the steel shanks, the longer the shank the more leverage it exerts. A 6 inch shank at 10 pounds of pressure applied by the hand is actually 180 lbs of pressure on the horses nose and chin.
I would just turn this big fellow out and let him rest a few months, then start riding again in a light snaffle and see what happens.